1,721,020 research outputs found
“MICRO X-RAY LAB”: A NEW APPROACH FOR HEAVY METAL SPECIATION IN POLLUTED SOILS AND ENVIRONMENTAL MATERIALS
No full textHeavy metals (HM) in soils can be toxic for cultivated plants and living organisms and can pose a serious risk for human health, especially if they can reach underground waters or enter the food chain. Determining HM total concentration in soil is only the starting point of a risk assessment, but nowadays information about HM speciation is crucial to understand the real impact of HM pollutants on the environment. In addition, soil is an extremely heterogeneous matrix where different organic and inorganic components are mixed down to the micrometer or nanometer scale. Therefore analytical instruments capable of resolving such a complexity at the nanometer/micrometer scale are also needed. To this purpose, a proper combination of X-ray analyses can provide both information about HM total concentration and speciation also at the nanometer/micrometer level.
At the University of Bari a new laboratory called "Micro X-ray Lab" has been created. In this lab, the potentialities of different X-ray based analytical techniques are combined to solve problems related to soil HM pollution and remediation. To this purpose the following instrumentation is available: a portable X-ray fluorescence spectrometer (pXRF) (for quick semiquantitative in situ analyses), a wavelength dispersive X-ray fluorescence spectrometer (WD-XRF) (for more precise determinations of HM in solid and liquid samples), a total reflection X-ray fluorescence spectrometer (TXRF) (for the determination of HM at ppb levels), a micro X-ray fluorescence spectrometer (μ-XRF) and a Variable Pressure Field Emission Scanning Electron Microscope (for the identification of HM pollutants at the micro/nano-scale). In addition, HM-containing mineral phases of soil samples are investigated by X-ray powder diffraction (XRPD) and thermogravimetrical and differential thermal analyses (TGA/DTA). Finally, X-ray microtomography (μ-CT) is used to characterize the soil structure, its porosity as well as the internal structure of microscopic soil minerals.
The same methodological approach can be applied to the study of HM in other environmental materials such as plant and biological matrices and to assess the efficacy of technologies developed for the remediation of HM polluted soils.
In this work, preliminary results on HM speciation and biaccessibility studies in polluted soils are presented and discussed with a focus on As-polluted soils. The aim of these studies are to identify the source and the fate of pollution as well as to develop suitable physical-chemical procedures to remediate the contaminated sites
UNTREATED PLANT WASTE OF THE MEDITERRANEAN REGION AS BIOADSORBENT OF PERSISTENT ORGANIC POLLUTANTS
Full text linkThe excessive and/or improper use of plant protection products (PPPs) can generate alarming levels of residues in the environment, compromising both soil fertility and food safety. Various organic wastes released in large amounts by agro-industrial activity are currently studied and applied as bioadsorbents for water and soil decontamination. This study explored the capacity of untreated orange peel, olive stones and pistachio shells to adsorb the PPPs oxyfluorfen (OXY), metribuzin (MET) and imidacloprid (IMI), and the xenoestrogen bisphenol A (BPA) from water. The physicochemical, microstructural, and spectroscopic characteristics of the adsorbents were first evaluated using TXRF, SEM and FTIR-ATR techniques. Adsorption kinetics showed that each pollutant was rapidly (∼ 24 h) retained by all adsorbents according to a pseudo-second order model, which suggested a prevalent chemisorption. Interpretation of the sorption isotherm data with various theoretical equations showed that all molecules on all adsorbents preferentially followed the Freundlich model. Among the materials, olive stones showed the highest adsorbent capacity with KF values equal to 713, 317, 359 and 736 mg kg-1 for OXY, MET, IMI, and BPA, respectively. The desorption of each compound from all materials was hysteretic. Based on the overall results obtained, it appears that all three materials tested may have interesting applications for the retention of organic pollutants, especially very hydrophobic ones. This paves the way for further investigations into natural adsorbents as sustainable tools for environmental remediation
The “Exultet 1” of Bari: multi-methodological approach for the study of a rare medieval parchment roll
No full textA rare medieval parchment roll, called Exultet 1 (first half of XI Century), preserved in the Diocesan Museum of Capitolo Metropolitano of Bari (Italy) has been studied. Certainly, it is one of the highest literary and artistic expressions ever produced in Bari, one of a kind. It is also the very first among medieval European liturgical rolls, in which miniatures are painted upside-down in respect to the text. To analyse inorganic pigments, a mobile laboratory has been set up at the museum. The techniques used, for a non-invasive and non-destructive in situ analysis, were: VIS-NIR spectrophotometry in reflectance mode with optic fibres (FORS), X-Ray fluorescence spectrometry (XRF) and finally μ-Raman spectroscopy. Such multi-methodological approach allowed to acquire many data without causing any stress to the artwork. The mineral pigments have been identified mainly by FORS and they are: red earth and minium, lapis lazuli and azurite, green earth and copper resinate, orpiment and yellow earth. In some areas, traces of a residual gold leaf have been identified by XRF. The presence of rare and precious pigments as lapis lazuli and gold leaf underlines the sacredness and the importance of the parchment. This is the first scientific investigation performed on the Exultet 1 of Bari
Suoli contaminati da As: l’importanza di speciazione e biodisponibilità per la valutazione del rischio reale
No full textQual è il rischio per la salute umana nell‟impiego di suoli contaminati da arsenico (As) in agricoltura o per il pascolo? Come è noto, non è tanto la concentrazione totale del contaminante a costituire di per sé una minaccia, quanto la sua distribuzione nelle diverse forme chimiche (speciazione), che ne influenza la frazione biodisponibile e quindi le sue possibilità di entrare nella filiera alimentare. E‟ in questa direzione che si muove il presente lavoro, volto a determinare il rischio reale che deriva dalla presenza di As in suoli campionati in aree pertinenti ad ex attività industriali (Scarlino, GR) e minerarie (Valle Anzasca, VB), con concentrazioni tra le decine ad alcune migliaia di ppm. È così stato adottato un duplice approccio, mirato ad ottenere da un lato una puntuale caratterizzazione chimico-mineralogica dei suoli stessi e quindi informazioni circa la speciazione dell‟As, dall‟altro a valutarne la biodisponibilità e l‟ecotossicità. Le analisi chimiche e mineralogiche dei suoli sono effettuate mediante tecniche che impiegano radiazione X; in particolare la caratterizzazione chimica in situ viene condotta tramite spettrometria di fluorescenza portatile con rivelatore a dispersione di energia (ED-pXRF), e in laboratorio mediante dispersione di lunghezza d‟onda (WD-XRF). In via preliminare esse hanno permesso di individuare nei suoli di Valle Anzasca una certa correlazione tre le concentrazioni rispettivamente di As e Fe e di As e S. La caratterizzazione mineralogica è invece condotta con un diffrattometro di raggi X su polvere (XRPD), introducendo corindone (Al2O3) come standard interno per la quantitativa. Non sono stati però rivelati minerali dell‟As, per via della loro scarsa concentrazione. Anche a questo proposito, sono in atto procedure di estrazione sequenziale (metodo Wenzel), per valutare la maggiore o minore mobilità dell‟As, ma pure ottenere informazioni complementari circa i minerali dell‟As presenti (ad esempio è stato individuato pentossido di As in un campione di Scarlino). Ulteriori dati circa la distribuzione dell‟As nei suoli vengono ottenuti per mezzo di una microfluorescenza di raggi X (ED-μXRF), effettuando scansioni dei suoli in sezione sottile. La biodisponibilità viene valutata utilizzando lombrichi epigeici della specie Eisenia andrei (Bouché), esposti a microcosmi contaminati e sottoposti ad analisi dei fluidi celomatici mediante TXRF e della distribuzione dell‟elemento nel corpo mediante ED-μXRF
A Study on the Characteristics of Buds and Flowers in Pomegranate: Differences among Cultivars
Full text linkThe growing cultivation of pomegranate and the interest of consumers in the nutraceutical properties of the fruit have not yet spurred similar increases in the knowledge base of some important botanical and physiological aspects of this species, such as bud differentiation. The aim of this research was to study the bud morphology of four pomegranate cultivars (‘Comune S. Giorgio’, ‘Wonderful’, ‘Ki-Zakuro’, and ‘Haku Botan’) to better clarify the bud differentiation process. In all four cultivars, the number and the position of the buds were variable, from a typical two buds per node to a single bud or more (3). Two types of buds were observed: small and thin on the twigs (short, medium, and long) and large and round on the spurs; large buds were also observed on twigs but in a reduced number. Flowers showed differences among the cultivars, with a larger number of petals in ‘ornamental’ cultivars because of the petaloidy. Hermaphrodite flowers were larger and longer than the staminate flowers and also more abundant. Moreover, flowers developing from a flower bud were longer than flowers developing from mixed buds. The presence of an undifferentiated meristem, starch grains in the protective scales, and two small transition leaves were observed in all the types of buds from summer to the end of endodormancy in all cultivars. However, a dome-shaped meristem was observed in a few flower buds. Our observations indicate pomegranate behaves as a species for warm, sub-tropical, and tropical areas more than for temperate ones
Laboratory-based X-ray multianalytical approach to assess the bioavailability of arsenic in contaminated soils
No full textArsenic (As) is a metalloid element, naturally associated with gold, sulphur, iron and heavy metals and is often found in soils around former mines and industrial sites treating As-bearing minerals. The assessment of the bioavailability of As in these soils is very important in order to protect human and ecosystem health. Earthworms are the most used organisms to assess the bioavailability of As in contaminated soils. The present work aims at evaluating the bioavailability of As in six polluted soils sampled in the industrial area of Scarlino (Tuscany, Italy) and the gold mining site of the Anzasca Valley (Piedmont, Italy), using Eisenia andrei as a bioindicator and a multianalytical X-ray based approach.
The soils were preliminary analysed in situ by portable energy dispersive X-ray fluorescence spectrometry (pEDXRF) which detected As concentrations ranging from 20 to 800 mg/kg in Scarlino, and from 20 to 20000 mg/kg in Anzasca Valley. X-ray powder diffraction (XRPD) detected no As-bearing mineral. Only in the most contaminated soil from Anzasca Valley, jarosite and goethite were detected as minerals formed as a consequence of the alteration of pyrite and arsenopyrite. In order to have more information about As speciation, micro X-ray fluorescence (μXRF) analysis were performed on soil thin sections, which showed the co-presence of Fe and As around quartz or feldspar grains. This is in accordance with the results of sequential extractions which indicated that As was mainly associated with amorphous and/or well-crystallized Fe oxides and hydroxides. To study As bioavailability, ten sexually mature earthworms were exposed to contaminated and control soils. After 14 days, mortality (which gives information about acute toxicity) and oxidative stress were measured. The chronic toxicity was estimated with reproduction tests after 28 days. μXRF analyses on earthworm thin sections revealed that As accumulates mainly in the coelomic cavity while no As was detected in other parts of the body. Given that As detoxification in earthworms seemed to involve mainly the coelom, coelomic fluids were electrically extruded and the As concentration was estimated via total-reflection X-ray fluorescence (TXRF) spectroscopy.
In all cases, no earthworm died after 14 days of exposure to contaminated soils even if an oxidative stress was measured. A chronic toxicity was observed after 28 days with a reduction in new born organisms with the increase of As concentration. TXRF analyses on coelomic fluids suggested that the As concentration in the fluids was closely related with the As available fraction (adsorbed or loosely bound to Fe oxides and hydroxides) and not with the total As concentration in soils. In fact, when a consistent part of the As was associated with well crystallized Fe-hydrous oxides (the low available fraction) the concentration of As in the coelomic fluids was comparable to that found in earthworms exposed to control soils. Finally, this study showed the usefulness of laboratory x-ray based techniques for bioavailability studies and could be used as a base for the development of new procedures for the assessment of As bioavailability in contaminated soils
Assessing chromium pollution and natural stabilization processes in agricultural soils by bulk and micro X-ray analyses
No full textA combined approach based on multiple X-ray analytical techniques and conventional methods was adopted to investigate the distribution and speciation of Cr in a polluted agricultural soil, from the bulk-scale down to the (sub)micro-level. Soil samples were collected from two different points, together with a control sample taken from a nearby unpolluted site. The bulk characterization revealed that the polluted soils contained much higher concentrations of organic matter (OM) and potentially toxic elements (PTE) than the control. Chromium was the most abundant PTE (up to 5160 g kg−1), and was present only as Cr(III), as its oxidation to Cr(VI) was hindered by the high OM content. According to sequential extractions, Cr was mainly associated to the soil oxidisable fraction (74%) and to the residual fraction (25%). The amount of Cr potentially bioavailable for plant uptake (DTPA-extractable) was negligible. Characterization of soil thin sections by micro X-ray fluorescence (μXRF) and field emission scanning electron microscopy coupled with microanalysis (FEGSEM-EDX) showed that Cr was mainly distributed in aggregates ranging from tens micrometres to few millimetres in size. These aggregates were coated with an aluminosilicate layer and contained, in the inner part, Cr, Ca, Zn, P, S and Fe. Hyperspectral elaboration of μXRF data revealed that polluted soils were characterised by an exogenous organic-rich fraction containing Cr (not present in the control), and an endogenous aluminosilicate fraction (present also in the control), coating the Cr-containing aggregates. Analyses by high-resolution micro X-ray computed tomography (μCT) revealed a different morphology of the soil aggregates in polluted soils compared with the control. The finding of microscopic leather residues, combined with the results of bulk- and micro-characterizations, suggested that Cr pollution was likely ascribable to soil amendment with tannery waste-derived matrices. However, over the years, a natural process of Cr stabilization occurred in the soil thus reducing the environmental risks
Occurrence of Arsenic in Soils and Paleosols of the Claromecó River Basin, Southern Pampean Plain (Argentina)
No full textThe Chacopampean plain is an extended flatland characterized by high As within sediments anddrinking waters. The volcanic glass shards, normally present as a major constituent of the Chacopampean plain sediments, are classically considered the main source of As. Nevertheless,
thick volcanic ash layers and Fe-Mn (Al) oxy-hydroxides are also contemplated as a reasonable
source of As in the sediments.
In order to understand the main source of As in the Claromecó river basin (southern
Chacopampean plain) sediments, paleosols, present-day soils and groundwaters were sampled.
Three sedimentological units were identified: a deeper early Pliocene fluvial unit (mean sediment
As~ 4.6 mg/kg), a shallower late Pleistocene fluvial unit (mean As ~ 11.6mg/kg) and Holocene
Loess (mean As~ 2.5 mg/kg). Two types of paleosols were characterized: a Pliocene pedogenic
calcrete (mean As∿ 3.6 mg/kg) and a Late Pleistocene hydromorphic paleosol (mean As∿ 16.5
mg/kg). The present-day soils were taken into account where mean As is ∿ 10.5 mg/kg. Although
mean values for each unit are quite different, statistical analyses (ANOVA) reveal no statistically
significant difference between As concentrations within the various sedimentological units.
However, the hydromorphic paleosols and present day soils show a statistically significant
difference from the rest of the units. In these pedogenetic units, the highest As concentrations
are located in the Fe-Mn(Al) oxy-hydroxide phases (nodules and rhizo-concretions) as shown by
sequential extractions and μ-XRF analysis. From this context, Pliocene pedogenic calcrete shows
low content of oxy-hydroxides and therefore low As. Additionally, As concentrations in waters
(mean As∿ 78.42 μg/L) shows higher values in shallower groundwaters coinciding with
Pleistocene paleosols.
This preliminary study highlights that the sediment deposition may not necessarily represent a
systematic control in the As concentrations even though an increment from the Pliocene to the
Holocene in sediment’s mean As values is noticed. However, the late Pleistocene hydromorphic
soils, most likely linked to a shift in the climatic conditions, favored the concentration of As within
Fe-Mn (Al) oxy-hydroxides phases. These pedogenetic features could represent the principal
source of As enrichment in groundwaters
Iron Oxides on Waste Steel Slags as Catalyst for the Transfer Hydrogenation of Nitrobenzene Using iso‐Propanol as Hydrogen Source
No full textIron oxide-based catalysts have been widely investigated due to their high catalytic activity and operational availability. However, in the perspective of commercial application, performance and cost are two crucial parameters for the development of catalysts. To reduce the cost, it is possible to use industrial wastes, such as steel slags, as effective support for iron oxide catalysts, which are also able to assist the catalytically active sites during their performances. Currently, steel slags are mainly used as building materials, nevertheless, sustainable reuse technologies are still desirable. Herein, the synthesis and characterization of several materials constituted of iron oxides onto steel slags in different mass ratio are reported. Their catalytic activity is also investigated in the reduction of nitrobenzene using iso-propanol as the hydrogen source in the absence of any added base
La microtomografia computerizzata di assorbiemnto di raggi X ad alta risoluzione come strumento di indagine nelle scienze agrarie ed alimentari
No full textLa micro-tomografia computerizzata di assorbimento di raggi-X (X-ray microCT) è una tecnica di imaging tridimensionale che consente di indagare la struttura interna di un campione in maniera non distruttiva. Nei comuni micro-tomografi da laboratorio il fascio conico di raggi-X (cone beam) emesso dalla sorgente radiogena incontra il campione rotante, e viene in parte assorbito ed in parte trasmesso, in maniera proporzionale al locale coefficiente di assorbimento μ (dove μ∝Z4). L’insieme delle proiezioni acquisite in corrispondenza di ciascuno step di rotazione del campione consente così una ricostruzione via software, che restituisce la distribuzione tridimensionale dei coefficienti di assorbimento nell’ambito dell’intero volume indagato.
Le applicazioni della microCT sono le più trasversali, dalla medicina alle scienze dei materiali, dalle geoscienze all’informatica e così via. Vedere dentro un oggetto senza doverlo distruggere (tanto più importante quando il campione a disposizione è limitato, di particolare interesse scientifico o prezioso), eseguire analisi quantitative di porosità, volumi, superfici, osservare modificazioni strutturali in corrispondenza di prove di carico o cambiamenti termici controllati, rendono di fatto la microCT sempre più indispensabile nei moderni laboratori.
In questa presentazione verranno mostrate alcune possibili applicazioni in campo Agrario, Ambientale ed Alimentare, ottenute mediante uno strumento da laboratorio con una risoluzione massima di 350 nm. In particolare, allo scopo di evidenziare alcune delle potenzialità della tecnica verranno mostrati i risultati relativi a campioni di:
Suolo: in base ai diversi valori di μ relativi alle frazioni principali, è possibile distinguerle e svelarne le caratteristiche morfometriche, quali volume, superficie, ecc. Laddove è presente un sufficiente contrasto fra le diverse componenti è anche possibile discriminare le diverse fasi mineralogiche, porosità e apparati radicali delle piante;
Biochar: ne può essere calcolata la porosità e la superficie attiva, parametri fondamentali per studiare il materiale come ammendante col suolo;
Semi: le strutture interne possono essere visualizzate e studiate senza "aprire" il seme;
Lombrichi: le caratteristiche morfologiche dell’organismo vengono mostrate con una risoluzione di pochi micron in modo da poter “entrare” nei diversi organi e visualizzarne una qualsiasi sezione;
Pane e prodotti da forno: può esserne determinata la struttura e la porosità al fine di migliorare la qualità del prodotto.
I diversi esempi evidenziano come la microCT sia uno strumento molto importante per le moderne indagini analitiche grazie sia alla possibilità di imaging in senso stretto, sia per analisi quantitative di tipo strutturale (es. porosità, area superficiale), consentendo in alcuni casi notevoli miglioramenti in termini di consumo di tempo e di qualità del dato rispetto ad altre metodologie analitiche tradizionali
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